1. Field of the Invention
The present invention generally relates to control systems for automotive vehicles. The present invention specifically relates to a control of automotive vehicles equipped with two or more active chassis systems with each chassis system capable of influencing vehicle behavior in the yaw plane of the automotive vehicle. Examples of such active chassis systems include, but are not limited to, an active brake control system, an active front steer system, an active rear steer system, an active front and rear steer system, and an active roll bar or active suspension system.
2. Description of the Related Art
Traditionally, vehicle motion was controlled in the yaw plane by using brakes and throttle to control longitudinal motion and steering for directional control. Over the last 20 years many active chassis systems have been developed for allowing the driver to control vehicle in the normal range of operation and for correcting vehicle behavior when it deviates significantly from desired behavior. The need for intervention usually occurs when driver inputs (e.g., steering, brake or throttle) are excessive for given surface and speed conditions. These systems typically operate in a closed loop (feedback) fashion. That is, in determining a corrective input, these systems compare the desired response of vehicle determined from the driver inputs to the measured response of the vehicle or the individual wheels. The corrective input is applied to vehicle to force the actual vehicle response to conform to the desired response as closely as possible. Examples of active chassis systems currently in production or under development are (1) brake control including Anti-Lock Braking System (ABS), Traction Control System (TCS) and Vehicle Stability Enhancement (VSE) functions), (2) active rear steer, (3) active front steer, and (4) controllable suspension including active roll bars. More recently, vehicles being developed and produced are equipped with two or more active chassis systems. Each of them may be capable of fulfilling the control objectives required by feedback correction, at least to some extent.
As such, when and to what extent each system should be activated to achieve an accurate corrective input must be addressed. Appropriate addressing this issue is complicated, because each of the active chassis control systems are developed independently and different physical quantities are used as corrective control signals in each system. Furthermore, effectiveness of each chassis system depends on the operating point of vehicle and tires. There is therefore a need for unified control method for overcoming the aforementioned shortcomings described herein.